Binary Search Tree Preorder , Postorder , Inorder Traversal

Algorithm

INPUT: ROOT IS POINTER TO THE ROOT NODE OF THE TREE
OUTPUT: ELEMENTS OF BINARY SEARCH TREE
DATA STRUCTURE: BINARY TREE USING LINKEDLIST

STEP 1: START
STEP 2: PRINT("ENTER THE ROOT NODE")
STEP 3: ROOT=GETNODE(NODE)
STEP 4: ROOT->DATA=ITEM
STEP 5: ROOT->LC=NULL
STEP 6: ROOT->RC=NULL
STEP 7: PRINT("ENTER THE REMAINING ELEMENTS:")
STEP 8: NEWNODE(ROOT,ITEM)
STEP 9: NEWNODE(ROOT,ITEM)
STEP 10: IF(PTR->DATA>ITEM)THEN
STEP 11: IF(PTR->LC=NULL)THEN
STEP 12: PTR->LC=GETNODE(NODE)
STEP 13: PTR->DATA=ITEM
STEP 14: PTR->RC=NULL
STEP 15: PTR->LC=NULL
STEP 16: ENDIF
STEP 17: ELSE
STEP 18: NEWNODE(PTR,ITEM)
STEP 19: ENDIF
STEP 20: IF(PTR->DATA<ITEM)
STEP 21: IF(PTR->RC=NULL)THEN
STEP 21: PTR->RC=GETNODE(NODE)
STEP 22: PTR->RC=NULL
STEP 23: PTR->LC=NULL
STEP 24: PTR->DATA=ITEM
STEP 24: ENDIF
STEP 25: ELSE
STEP 26: NEWNODE(PTR,ITEM)
STEP 27: ENDIF
STEP 28: END

Code

#include <stdio.h>
#include <stdlib.h>
struct node
{
    int data;
    struct node *lc;
    struct node *rc;
};
char ch;
int n;
int item;
struct node *news, *node1, *node2, *ptr1;
struct node *newnode(struct node *, int);
struct node *getnode();
struct node *postordertraversal(struct node *);
struct node *preordertraversal(struct node *);
struct node *inordertraversal(struct node *);
int main()
{
    struct node *tree;
    tree = malloc(sizeof(struct node));
    printf("ENTER THE ROOT NODE");
    scanf("%d", &tree->data);
    // tree->lc = NULL;
    // tree->rc = NULL;
    // printf("ENTER THE ELEMENTS AND -1 FOR EXIT");
    ptr1 = tree;
    n = tree->data;

    while (n != -1)
    {

        printf("ENTER THE VALUE OF NODE %d :", n);
        scanf("%d", &n);
        newnode(tree, n);
    }

    printf("preorder Traversal: ");
    preordertraversal(tree);
    printf("\n");
    printf("inorder traversal: ");
    inordertraversal(tree);
    printf("\n");
    printf("postorder traversal: ");
    postordertraversal(tree);
    return 0;
}
struct node *newnode(struct node *ptr, int n)
{
    // if(ptr==NULL)
    // {
    // ptr=malloc(sizeof(struct node));
    // }
    // printf("%d", ptr->data);
    // printf("ENTER THE VALUE OF NODE %d :", n);
    // scanf("%d", &n);
    if (n == -1)
    {
        return 1;
    }
    if (ptr->data > n)

    {
        if (ptr->lc == NULL)
        {

            // if (ptr->lc == NULL)
            // {
            struct node *news = malloc(sizeof(struct node));
            ptr->lc = news;
            ptr = news;
            news->data = n;
            // ptr->data=news->data;
            // ptr->lc = NULL;
            // ptr->rc = NULL;
            // }
        }

        else
        {
            newnode(ptr->lc, n);
        }
    }
    // printf("DOES TREE %d HAS RIGHT CHILD Y/N : ",n );
    // scanf("%c", &ch);
    else if (ptr->data < n)
    {
        if (ptr->rc == NULL)
        {
            struct node *news = malloc(sizeof(struct node));
            ptr->rc = news;
            // ptr = ptr->rc;
            ptr = news;
            news->data = n;
            // ptr->lc = NULL;
            // ptr->rc = NULL;
        }

        else
        {
            newnode(ptr->rc, n);
        }
    }
}
struct node *getnode(int n)
{
    news = malloc(sizeof(struct node));
    // news->data=n;
    return news;
}
struct node *preordertraversal(struct node *root)
{
    if (root == NULL)
        return root;
    printf("%d ", root->data);
    preordertraversal(root->lc);
    preordertraversal(root->rc);
}
struct node *inordertraversal(struct node *root)
{
    if (root == NULL)
        return root;
    inordertraversal(root->lc);
    printf("%d ", root->data);
    inordertraversal(root->rc);
}
struct node *postordertraversal(struct node *root)
{
    if (root == NULL)
        return root;
    postordertraversal(root->lc);
    postordertraversal(root->rc);
    printf("%d ", root->data);
}

Output

user@computer$ : ENTER THE ROOT NODE28
ENTER THE VALUE OF NODE 28 :42
ENTER THE VALUE OF NODE 42 :18
ENTER THE VALUE OF NODE 18 :17
ENTER THE VALUE OF NODE 17 :23
ENTER THE VALUE OF NODE 23 :13
ENTER THE VALUE OF NODE 13 :85
ENTER THE VALUE OF NODE 85 :36
ENTER THE VALUE OF NODE 36 :19
ENTER THE VALUE OF NODE 19 :81
ENTER THE VALUE OF NODE 81 :55
ENTER THE VALUE OF NODE 55 :-1
preorder Traversal: 28 18 17 13 23 19 42 36 85 81 55 
inorder traversal: 13 17 18 19 23 28 36 42 55 81 85 
postorder traversal: 13 17 19 23 18 36 55 81 85 42 28